Ditto what John EB mentioned. MEP is quite different from Pinnacle (which I also use occasionally) and where everything is and what it does is not all that obvious. Best to read the manual. I usually have F1 open.
I missed one other method that is quick and useful if you just want the image inserted on the timeline.
Right-click on the object where you want to create a still image, select Create still frame.
This cuts the video at this point makes a still image of the frame extending the length of the remaining right side part of the video clip. The video portion to the right is removed. The image can be resized. Thus if the frame that you want is at 5s of a 15s clip, the last 10s will be replaced by the still image.